1. Field of the Invention
The present invention relates to a method for measuring the optical properties in the region from the skin surface to the microcirculation system which is affected by hemoglobin, melanin, and the like, and of thereby measuring the surface state of the skin.
2. Description of the Related Art
Methods known in the past as methods for measuring and evaluating skin pigmentation, discoloration, and the like include the method in which light having a specific wavelength is allowed to be incident on the skin surface, the reflected light is received, and the skin reflectance at a specific wavelength is determined, thereby allowing erythema or pigmentation to be evaluated (Japanese Unexamined Patent Application 58-33153). In another known method for measuring skin pigmentation, the ratio of reflectance on the skin at two specific wavelengths is measured, so as to determine the index relating to the melanin content or hemoglobin content (Japanese Unexamined Patent Application 5-161609).
Yet another known method for measuring the epidermal hue that are unaffected by blood is the method in which the skin surface is drawn and partially pulled up, white light is allowed to be incident on that part, and the spectral spectrum of the transmitted light on the epidermal is determined (Japanese Unexamined Patent Application 5-87730).
Problems in the aforementioned methods for measuring the reflected light on skin, however, are that the light which is received includes a great deal of surface scattered light in addition to internal scattered light in the skin, resulting in significant variation in the optical path length of the received light, which makes accurate analysis impossible.
Problems in the method for detecting transmitted light on the epidermal are that the detected results are not affected by blood, making it impossible to evaluate the degree of skin color affected by blood circulation.
An object of the present invention is to resolve the aforementioned disadvantages of the conventional technology, allowing better evaluation of the optical properties of skin, such as discoloration and shading in which the microcirculation of the blood and melanin deposition are involved.